The present invention relates to a clamping contact connection for the electrical connection of a fetal scalp electrode to a leg plate fixable to the expectant mother.
In order to record the heart rate of the unborn fetus before and during birth, use is made of scalp electrodes, which are provided on the side thereof facing the fetus head with one or two spiral wires, which are turned into the fetal scalp. For this purpose use is normally made of a vaginal introduction aid with an inner and an outer tube, which facilitates the application of the scalp electrode. The electrode head with the spiral wire or some other fastening means is located in the outer tube at its end facing the fetus. The electrode head and the inner tube have a nonrotary, but detachable connection.
For applying the electrode the doctor firstly guides the outer tube into the birth canal until it contacts the scalp of the fetus. Whilst holding the outer tube the other hand is used for sliding forwards the inner tube until the spiral wire fitted to the electrode head comes into contact with the head of the fetus. Subsequently the inner tube is turned, so that the spiral electrode perforates the fetal scalp and penetrates the same. The inner tube can now be retracted, because the electrode head and the inner tube are not fixed to one another in the axial direction. Subsequently the outer tube is also retracted. Scalp electrodes and introduction mechanisms are known per se and are frequently mentioned in patent literature, e.g. in U.S. Pat. Re. No. 28 990, U.S. Pat. No. 4,301,806 or DE 4,228,351 C1.
The connecting wire of the electrode head is guided through the inner tube and following the drawing out of the two tubes remains in the birth canal and is then connected to a corresponding monitoring instrument, e.g. a cardiotocograph. For this purpose the connecting wires are connected to a so-called maternal leg plate, which is fixed to the leg of the expectant mother. The maternal leg plate is essentially a small box with a conductive base, which produces a galvanic contact with the body of the mother and is intended to prevent extreme potential fluctuations. In turn the leg plate is connected by a cable to the cardiotocograph.
The connection of the wires to the leg plate must be such that an the one hand a reliable electrical contact is provided, but on the other so that the connection can be rapidly detached, so that during birth the relatively heavy leg plate does not tear the spiral electrode out of the scalp of the baby and consequently cause serious injury. In addition, it must be easy to clean the leg plate, because it is fixed to the thigh of the mother and consequently during birth comes into contact with blood or other body liquids. The electrical connection of the leg plate and wire ends must be such that it can be brought about with a minimum of manipulations. In addition, the risk of an erroneous connection to sockets carrying mains voltage must be prevented. The contacting device on the wires of the scalp electrode must pass through the introduction tube, because the latter is, as stated, retracted after fitting.
Hitherto clamping devices have been fitted to the leg plate and in these are clamped already insulated ends of the wires. In this case one hand must be used for operating the clamping device and the other for introducing the wire into the clamping device. For the clamping device the leg plate must be movable and/or have parts sliding on one another. These transitions or junctions are generally difficult to clean, because liquid can be deposited by capillary action and is very difficult to remove. If they come into contact with the mains voltage, the free wire ends can endanger the baby and/or mother. Another connection of the scalp electrode to the leg plate is known from EP 484,107 A1, in which a plug or a socket is connected to the wire ends of the scalp electrode and is then connected to a corresponding counterpart in the leg plate. Although with this plug connection a very simple connection of electrode and leg plate can be obtained by plugging action, the contacts are free and can dome into contact with parts carrying the mains voltage. There is a dirtying risk as a result of the openings in the leg plate for receiving the plug or the socket and said openings are not easy to clean.
The problem of the present invention is therefore to propose a detachable electrical connection of the scalp electrode to the leg plate, which is improved compared with the prior art with respect to fitting, detachability, cleaning and safety.